Reduction of power consumption in memory devices during refresh modes

ABSTRACT

Devices, systems, and methods include an active mode to accommodate read/write operations of a memory device and a self-refresh mode to accommodate recharging of voltage levels representing stored data when read/write operations are idle. At least one register source provides a first voltage level and a second voltage level that is less than the first voltage level. With such a configuration, during the active mode, the memory device operates at the first voltage level as provided by the at least one register source, and during the self-refresh mode, the memory device operates at the second voltage level as provided by the at least one register source.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is continuation of U.S. patent application Ser.No. 15/181,358, filed on Jun. 13, 2016, which is a divisional of U.S.patent application Ser. No. 13/997,959, filed on Dec. 19, 2013, whichclaims the benefit of priority to International Application No.PCT/US2012/030657, filed on Mar. 27, 2012, the entire contents of theseapplications are incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to the field of integrated circuitsand, more particularly, to devices and systems that reduce power usageof memory.

BACKGROUND ART

As electronic and computing devices evolve to provide more functionalityand process more content, such devices demand larger storage capacitieswhile, at the same time, increased power efficiency. Given their storageand bandwidth capacities, many electronic and computing devices employdynamic random access memories (DRAMs) as the working memory of thesedevices.

Although there are multiple types and variations of DRAMs, most DRAMsrequire regular or periodic refreshing of the voltage levels in thecells of the DRAMS to retain the corresponding logic data storedtherein. This is due to certain parasitic effects and leakage currentsin the memory cells of the DRAMs which may, over time, degrade thestored voltage levels. Refresh operations occur during standby periodsin which read/write operations to/from the DRAMs are idle. DRAMstypically have a self-refresh mode which, in concert with the standbyperiod, involves turning off internal clocks and input channels whileproviding a clock enable (CKE) signal, issued by the memory controller,to trigger the self-refresh mode.

However, the increased functionality of electronic and computingdevices, as noted above, presents certain challenges in reducing thepower consumption of such memory devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a high-level functional block diagram of a systemconfigured to reduce power consumption of memory devices during standbymodes, in accordance with various aspects of the present disclosure.

FIG. 2 depicts a timing diagram representing reduction in powerconsumption of memory devices, in accordance with various aspects of thepresent disclosure.

DETAILED DESCRIPTION

In the description that follows, like components have been given thesame reference numerals, regardless of whether they are shown indifferent embodiments. To illustrate an embodiment(s) of the presentdisclosure in a clear and concise manner, the drawings may notnecessarily be to scale and certain features may be shown in somewhatschematic form. Features that are described and/or illustrated withrespect to one embodiment may be used in the same way or in a similarway in one or more other embodiments and/or in combination with orinstead of the features of the other embodiments.

In accordance with various embodiments of this disclosure, what ispresented are devices, systems, and methods that include an active modeto accommodate read/write operations of a memory device and aself-refresh mode to accommodate recharging of voltage levelsrepresenting stored data when read/write operations are idle. At leastone register source provides a first voltage level and a second voltagelevel that is less than the first voltage level. With such aconfiguration, during the active mode, the memory device operates at thefirst voltage level as provided by the at least one register source, andduring the self-refresh mode, the memory device operates at the secondvoltage level as provided by the at least one register source. In thismanner, the consumption of power by the memory device is reduced duringthe self-refresh mode, thereby improving the overall power efficiency ofthe memory device.

These and other features and characteristics, as well as the methods ofoperation and functions of the related elements of structure and thecombination of parts and economies of manufacture, will become moreapparent upon consideration of the following description and theappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification, wherein like reference numeralsdesignate corresponding parts in the various figures. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration and description only and are not intended as a definitionof the limits of claims. As used in the specification and in the claims,the singular form of “a”, “an”, and “the” include plural referentsunless the context clearly dictates otherwise.

Turning attention to the figures, FIG. 1 depicts a high-level functionalblock diagram of system 100 having a memory device with self-refreshmode capabilities, in accordance with various aspects of the presentdisclosure. System 100 represents any of a number of electronic and/orcomputing devices that may include a memory device with a self-refreshmode. Such electronic and/or computing devices may include servers,desktops, laptops, mobile devices, smartphones, gaming devices, tabletcomputers, networking devices, etc.

In the depicted embodiment, system 100 includes memory device 110,processor 140, memory controller 130, voltage regulator 170, and serialpresence detect 180. In alternative embodiments, system 100 may includemore components, fewer components, and/or different components.Moreover, although system 100 is depicted as comprising separateelements, it will be appreciated that such elements may be integratedonto one platform.

Memory device 110 provides, at least in part, the main system memory forsystem 100. Memory device 110 may comprise a DRAM device, such as, forexample, DDR1, DDR2, DDR3, DDR4, LPDDR, etc., in accordance with any ofthe embodiments described herein. Memory device 110 may include one ormore memory resources 112 a-112 n. Memory resources 112 a-112 nrepresent the resources on which the data is stored for memory 110,sometimes referred to as the memory array. In different embodiments, thememory resources may be configured as separate memory channels, memorybanks, memory groups, etc.

Memory device 110 includes self-refresh (SR) controller 120, whichrepresents hardware and/or software logic within memory 110 to implementself-refresh operations. As mentioned above, self-refresh operations areadministered within the memory device itself, which includes SR control120 to implement the state changes and trigger the self-refresh mode.

Memory device 110 further comprises mode register(s) 150 andmultipurpose register 160. Mode register(s) 150 is capable of storingsystem configuration parameter settings/values, in predefined registersof certain bit lengths, in order to define the capabilities of system100. Depending on the DRAM type embodied by memory device 110, thestored configuration parameter settings may be programmable i.e.,read/writeable or they may be hard-coded i.e., read-only.

In addition, multipurpose register 160 is also capable of storing, amongother things, system configuration parameter settings/values that definethe capabilities of system 100. The stored configuration parametersettings may be programmable i.e., read/writeable.

System 100 further includes processor 140, which represents theprocessing resources of system 100. As the processing resource,processor 140 is depicted as being communicatively coupled to memorydevice 110 via bus infrastructure 142 and voltage regulator 170 via achannel infrastructure 174. It will be appreciated that processor 140may communicate with other components of system 100, but in the interestof clarity, such communications are omitted without any loss in theunderstanding of the principles of operation disclosed herein.

It will also be appreciated that, while shown as a singular unit,processor 140 may include one or more processor devices including one ormore microprocessors or microcontrollers as well as multi-coreprocessing devices. Processor 140 accesses memory device 110 over a businfrastructure 142 to perform read and write operations. In someembodiments, bus 142 may also be routed through memory controller 130.

Consistent with various implementations and for the sake of simplicity,memory controller 130 is shown to be integrated with processor 140, inaccordance with an embodiment of the present disclosure. However, itshould be appreciated that, depending on certain implementations, memorycontroller 130 may not be integrated with processor 140 and may becommunicatively coupled to processor 140 via a bus infrastructure.

Memory controller 130 is configured with logic (hardware and/orsoftware) to control access to memory device 110. Additionally, memorycontroller 130 includes logic to generate the self-refresh operations.As depicted, memory controller 130 accesses memory device 110 via businfrastructure 142 and is capable of providing a clock enable (CKE)signal to memory device 110, which indicates a transition toself-refresh mode.

As noted above, processor 140 communicates with voltage regulator 170via channel 174. The circuitry of voltage regulator 170 is configured toregulate a received voltage from a power supply to output a constant DCvoltage signal level commensurate with the voltage requirements ofsystem 100 components, such as, memory device 110, processor 140, memorycontroller 130, etc. As illustrated in FIG. 1, the regulated outputvoltage is supplied to memory device 110 via a supply lineinfrastructure 172, i.e., voltage rail.

System 100 also includes a serial presence detect (SPD) module 180. TheSPD 180 typically comprises an EEPROM device coupled to the DIMM ofmemory device 110 that stores operational information of system 100 tothe BIOS. The operational information is stored in read-only form andduring the BIOS process such information may be supplied to other system100 components, such as, memory controller 130, memory device 110, moderegister(s) 150, and multipurpose register 160.

As noted above, during standby periods in which read/write operationsto/from the DRAMs are inactive or idle, the DRAMs may enter into aself-refresh mode. During the self-refresh mode, the voltage levels ofthe DRAM cells are refreshed or recharged to retain the correspondinglogic data stored therein. However, refreshing operations draw lesscurrent than active read/write operations. As such, the voltagessupplied to DRAMs during self-refresh modes may be reduced, whichresults in the overall memory power usage efficiency.

For example, in a non-limiting embodiment, memory device 110 of system100 may be configured as a dual data rate DRAM device, such as, DDR4.Typically, for both active and standby modes (including the self-refreshmode), DDR4 DRAMs require a regulated voltage Vdd of 1.2V with atolerance range of +/−5%. However, the current required to driverefreshing operations during the self-refresh mode is less than thecurrent required during active read/write operations. As such, anopportunity exists to reduce or lower the regulated voltage levelsupplied by voltage regulator 170 to memory device 110 during theself-refresh mode, without compromising data retention.

So, for the non-limiting embodiment in which memory device 110 comprisesa DDR4 DRAM, depending on manufacturer specifications, memory device 110may be supplied with a regulated voltage during self-refresh mode(VDD_SR) of 1.1V or 1.0V. Equally notable, the tolerance range of VDD_SRmay also be refined depending, again, on manufacturer specifications.For example, under one specification, memory device 110 may be suppliedwith a VDD_SR of 1.0V with a tolerance range of +/−4.0% while underanother specification, memory device 110 may be supplied with a VDD_SRof 0.98V with a tolerance range of +/−3.0%. It should be appreciated,however, that while the VDD_SR and refined tolerance values disclosedabove may be representative, they are not intended to be limiting in anyway.

With this said, VDD_SR and refined tolerance values may be implementedin system 100 by exploiting existing register resources that storeoperational and/or configuration setting information. In particular,depending on the DRAM type embodied by memory device 110, certainassociated register resources may enable the provision of VDD_SR andrefined tolerance values.

For example, in certain non-limiting embodiments, multipurpose register160, which stores system configuration parameter settings, may be usedto specify VDD_SR and refined tolerance values for DDR4 DRAMs. In otherembodiments, mode register 150, which also stores system configurationparameter settings may be used to specify VDD_SR and refined tolerancevalues for LPDDR DRAMs. In yet other embodiments, SPD module 180, whichstores operational information, may also be used to provide VDD_SR andrefined tolerance values.

With such a configuration, the VDD_SR and/or refined tolerance valuesmay be read from the register resources, namely, mode register 150,multipurpose register 160, and SPD module 180, and supplied to voltageregulator 130 during, for example, the BIOS process, to provide thelower voltage and tighter tolerance value during the self-refresh mode.In so doing, the consumption of power is reduced during self-refreshmode, thereby improving the overall power efficiency of memory device110.

By way of illustration, FIG. 2 depicts timing diagram 200, which 200illustrates the timing and triggering events for various signals memorydevice 110 signals, in accordance with various aspects of the presentdisclosure. In keeping with the non-limiting example noted above forclarity, memory device 110 may comprise a DDR4 DRAM device capable ofexecuting a self-refresh mode.

As illustrated in FIG. 2, differential clock signals (CK_t, CK_c), whichprovide the overall timing of system 100, are shown with certain timingpoints, such as, T0, T1, T2 . . . Ta0, Tb0 . . . Tf0, TSRE, TSRX, TVDD,and TVDD_SR. Clock enable (CKE) is the unidirectional signal provided bymemory controller 130 to trigger memory device 110 to enter self-refreshmode.

As shown, a deselect command (DES) signal is issued at T0, indicating noensuing active read/write operations for memory device 110; in otherwords, memory device 110 is to be in standby mode. As such, inaccordance with the CKE signal transitioning to a low level at timing T1and a self-refresh enable (SRE) command at timing T1, memory device 110enters into self-refresh mode shortly thereafter at timing TSRE with aself refresh enable clock count (tCKSRE).

After a certain number of clock cycles post SRE command, at timingTVDD_SR, voltage regulator 170 switches the regulated voltage suppliedto memory device 110 from the VDD voltage to the lower VDD_SR voltagespecified by the register resources. Consistent with the principlesdescribed above, VDD is the voltage signal level for active read/writeoperations, for example, in the case of DDR4 DRAM, VDD=1.2V; whileVDD_SR is the voltage signal level that is lower than VDD and stillcapable of supporting refreshing operations during the self-refreshmode, for example, VDD_SR=1.0V.

Moreover, in some embodiments, the switching of voltage signal levels byvoltage regulator 170 may be accomplished by adjusting voltage regulator170 to output the lower VDD_SR voltage. In other embodiments, voltageregulator 170 may provide two voltage signal lines (i.e., voltagerails), one supplying VDD and the other supplying lower VDD_SR. In thismanner, the switching of voltage signal levels may be achieved by havingvoltage regulator 170 toggle between the two voltage rails.

Memory device 110 will execute refresh operations at the lower voltagelevel VDD_SR and will continue to do so, until just prior to exitingself-refresh mode, noted as timing TVDD. That is, to prevent anypotential risk of data loss within memory device 110, prior to exitingthe self-refresh mode, a self-refresh exit clock count (tCKSRX) isgenerated internal to memory controller 130. It is during the tCKSRXclock count that a self-refresh exit (SRX) command and the CKE signal ofmemory controller 130 transitions to a high level, both indicating theapproaching end of the self-refresh mode. Therefore, as shown in FIG. 2at timing TVDD, within the tCKSRX clock count in which the SRX commandissues and the CKE signal transitions, voltage regulator 170 switchesthe regulated voltage supplied to memory device 110 back to VDD, priorto the exit of the self-refresh mode at TSRX.

As such, the consumption of power is reduced during self-refresh mode,thereby improving the overall power efficiency of memory device 110.

Having thus described the novel concepts and principles of theoptimization of carrier recovery performance, it will be apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications will occur and are intended to those skilled in the art,though not expressly stated herein. The alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary aspects of this disclosure.Additionally, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations therefore, is notintended to limit the claimed processes and methods to any order exceptas can be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful aspects of the disclosure, it is to be understood thatsuch detail is solely for that purpose, and that the appended claims arenot limited to the disclosed aspects, but, on the contrary, are intendedto cover modifications and equivalent arrangements that are within thespirit and scope of the disclosed aspects.

What is claimed is:
 1. A memory device comprising: a memory array; andcircuitry to: operate from a first voltage rail in a first mode, whereinthe first voltage rail is to provide a first DC voltage at a firstmagnitude, and wherein the first mode is to accommodate read and writeoperations to access the memory array, operate from a second voltagerail in a second mode based at least in part on a register, wherein thesecond voltage rail is to provide a second DC voltage at a secondmagnitude that is lower than the first magnitude, and wherein the memorydevice is to perform self-refresh in the second mode.
 2. The memorydevice of claim 1, further comprising: the register to store a value toindicate whether the memory device is to operate from the first orsecond voltage rail.
 3. The memory device of claim 1, wherein theregister comprises a mode register or a multipurpose register.
 4. Thememory device of claim 1, wherein a voltage regulator is to supplyvoltage to the first and second voltage rails to the memory device. 5.The memory device of claim 1, wherein: the circuitry is to be switchedfrom the first voltage rail to the second voltage rail based in part ona transition to the second mode.
 6. The memory device of claim 1,wherein: the circuitry is to be switched from the first voltage rail tothe second voltage rail based in part on the register.
 7. The memorydevice of claim 1, wherein: the circuitry is to be switched from thefirst voltage rail to the second voltage rail based at least in part ona second register, wherein the second register is to indicate whetheroperation from the second voltage rail is enabled.
 8. A methodcomprising: operating circuitry of a memory device from a first voltagerail in a first mode, wherein the first voltage rail is to provide afirst DC voltage at a first magnitude, and wherein the first modeaccommodates read and write operations; transitioning to a second mode,wherein the memory device is to perform self-refresh operations in thesecond mode; and operating the circuitry of the memory device from asecond voltage rail in the second mode based at least in part on aregister, wherein the second voltage rail is to provide a second DCvoltage at a second magnitude that is lower than the first magnitude. 9.The method of claim 8, comprising: causing a switch from the firstvoltage rail to the second voltage rail is based at least in part on atransition to the second mode.
 10. The method of claim 8, wherein:causing a switch from the first voltage rail to the second voltage railis based at least in part on the register.
 11. The method of claim 8,wherein: causing a switch from the first voltage rail to the secondvoltage rail is based at least in part on a second register, wherein thesecond register is to indicate whether operation from the second voltagerail is enabled.
 12. The method of claim 8, further comprising: storinga value in the register to indicate whether the memory device is tooperate from the first or second voltage rail.
 13. The method of claim12, wherein the register comprises a mode register or a multipurposeregister.